Semiconductor light-emitting device and method

ABSTRACT

The present invention discloses a semiconductor light-emitting device including a semiconductor light-emitting element, a first attaching layer and a wavelength conversion structure. The primary light emitted from the semiconductor light-emitting element enters the wavelength conversion structure to generate a converted light, whose wavelength is different form that of the primary light. In addition, the present invention also provides the method for forming the same.

RELATED APPLICATIONS

This application is a Continuation application of U.S. application Ser.No. 12/216,848 filed on Jul. 11, 2008 now U.S. Pat. No. 7,906,792, whichclaims the right of priority based on TW patent application, Ser. No.096125838, entitled “SEMICONDUCTOR LIGHT EMITTING DEVICE AND METHOD”,filed on Jul. 12, 2007, the disclosure of which is incorporated hereinby reference in its entirety.

TECHNICAL FIELD

The present invention relates to a semiconductor light-emitting device,and more particularly, to a semiconductor light-emitting device having awavelength conversion structure.

BACKGROUND

A light emitting diode (LED) is a solid-state semiconductor elementincluding at least a p-n junction. The p-n junction is formed between ap-type and an n-type semiconductor layers. When the p-n junctionreceives a suitable forward voltage, the holes of the p-typesemiconductor layer and the electrons of the n-type semiconductor layerare combined to emit light. Generally, the region emitting light iscalled a light-emitting region.

The characteristics of LEDs are small dimension, high lightingefficiency, long lifetime, quick reaction, high reliability, and greatchromaticity, so LEDs have been applied widely in electronic devices,motor, signboard, and traffic signals. With its full color spectrum, LEDhas gradually replaced conventional lighting apparatus such asfluorescent lamps and incandescent lamps.

Generally, a LED chip is utilized with a wavelength-converted materialsuch as phosphor to generate white light. The wavelength-convertedmaterial can emit yellow light, green light, or red light afterreceiving blue light from the LED chip, and then blue light and yellowlight, green light, or red light can be mixed to generate white light.Because the emitting direction of light is omnidirectional to ensurethat light from an LED chip can pass the wavelength-converted materialand be mixed to generate the desired light, the wavelength-convertedmaterial has to totally cover the positions where light emits. If thewavelength-converted material does not totally cover where light emitsout of the LED chip, a portion of light such as side-emitting light doesnot pass the wavelength-converted material and the wavelength convertingefficiency is reduced. On the other hand, although thewavelength-converted material totally covering the LED chip can increasewavelength-converting efficiency, it causes some problems like poor heatdissipation.

It is not easy to cover the LED chip uniformly with thewavelength-converted material. And because thicker wavelength-convertedmaterial receives more light than thinner wavelength converted materialdoes, the chromaticity of light is different when the omnidirectionallyemitted light passes the wavelength-converted materials of differentthickness. Although there are a lot of complicated methods such aselectrophoresis which is able to coat the wavelength-converted materialon the LED chip uniformly, the manufacturing cost is higher or the yieldis lower. In addition, the wavelength-converted material normally has tobe formed with an adhesive material like glue so it is unavoidable thatmuch of light is absorbed by the adhesive material and thewavelength-converting efficiency is therefore damaged.

SUMMARY OF THE DISCLOSURE

The present invention provides a semiconductor light-emitting deviceincluding an opaque substrate, a semiconductor light-emitting stackwhich emits a primary light, a first attaching layer, and a wavelengthconversion structure, wherein the semiconductor light-emitting stack isattached to the wavelength conversion structure by the first attachinglayer. The wavelength conversion structure receives the primary lightfrom the semiconductor light-emitting stack and then generates aconverted light whose wavelength is different from that of the primarylight. In addition, there is at least a reflective layer or atransparent conductive layer in-between the opaque substrate and thesemiconductor light-emitting stack.

The present invention also provides a method manufacturing asemiconductor light-emitting device, including forming a semiconductorlight-emitting stack on an opaque substrate, and attaching a wavelengthconversion structure to the semiconductor light-emitting stack by asecond attaching layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view of a semiconductor light-emittingdevice in accordance with an embodiment of the present invention.

FIG. 2 shows a cross-sectional view of a wavelength conversion structurein accordance with an embodiment of the present invention.

FIG. 3 shows a cross-sectional view of a semiconductor light-emittingelement in accordance with an embodiment of the present invention.

FIG. 4 shows a cross-sectional view of a semiconductor light-emittingstructure in accordance with an embodiment of the present invention.

FIG. 5 shows a cross-sectional view of a wafer in accordance with anembodiment of the present invention.

FIG. 6 shows a cross-sectional view of a semiconductor light-emittingdevice in accordance with another embodiment of the present invention.

FIG. 7 shows a cross-sectional view of a semiconductor element inaccordance with another embodiment of the present invention.

FIG. 8 shows a cross-sectional view of a semiconductor light-emittingdevice in accordance with another embodiment of the present invention.

FIG. 9 shows a cross-sectional view of a semiconductor light-emittingstructure in accordance with another embodiment of the presentinvention.

FIG. 10 shows a cross-sectional view of a wafer in accordance withanother embodiment of the present invention.

FIG. 11 shows a cross-sectional view of a semiconductor light-emittingdevice in accordance with another embodiment of the present invention.

FIG. 12 shows a cross-sectional view of a semiconductor element inaccordance with another embodiment of the present invention.

FIG. 13 shows a cross-sectional view of a transient substrate and atemporary attaching layer in accordance with an embodiment of thepresent invention.

FIG. 14 shows a cross-sectional view of FIG. 12 attached to a structureshown in FIG. 13.

FIG. 15 shows a cross-sectional view of FIG. 14 after removing a growthsubstrate and forming a transparent conductive layer.

FIG. 16 shows a cross-sectional view of FIG. 15 attached to an opaquesubstrate.

FIG. 17 shows a cross-sectional view of a wavelength conversionstructure in accordance with another embodiment of the presentinvention.

FIG. 18 shows a cross-sectional view of a semiconductor light-emittingstructure in accordance with another embodiment of the presentinvention.

FIG. 19 shows a cross-sectional view of a wafer in accordance withfurther another embodiment of the present invention.

FIG. 20 shows a schematic view of a light source device including asemiconductor light-emitting device of the present invention.

FIG. 21 shows a schematic view of a backlight unit including asemiconductor light-emitting device of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, in the present embodiment, a semiconductorlight-emitting device 1 includes a semiconductor light-emitting element10; a first attaching layer 13; and a wavelength conversion structure22, wherein the semiconductor light-emitting element 10 includes asemiconductor light-emitting stack 12 and an opaque substrate 11. Thesemiconductor light-emitting stack 12 is located on the opaque substrate11 and includes a buffer layer 121, an n-type semiconductor layer 122,an active layer 123, a p-type semiconductor 124, and a contact layer125. The material of the active layer 123 includes II-VI groupsemiconductor, III-V group semiconductor such as AlGaInP, AlGaInN,InGaN, SiC, ZnCdSe, or the combination thereof. The materials of thecontact layer 125, the n-type semiconductor layer 122, and the p-typesemiconductor layer 124 include II-VI group semiconductor, III-V groupsemiconductor, SiC, ZnCdSe, the combination thereof, or other materialsmatching with the active layer 123. The positions of the n-typesemiconductor layer 122 and the p-type semiconductor layer 124 areunrestricted to aforementioned description and can be changed accordingto requirement. The material of the opaque substrate 11 can besemiconductor material, metal material, composite material, or thecombination thereof. Preferably, it includes semiconductor, metal, Si,IP, ZnSe, MN, GaAs, Metal Matrix Composite (MMC), Ceramic MatrixComposite (CMC), or the combination thereof. The opaque substrate 11further includes a Distributed Bragg Reflector (DBR) layer locatedthereon and can have high heat-dissipation efficiency.

The wavelength conversion structure 22 is located on the first attachinglayer 13, covers approximately the whole top surface of thesemiconductor light-emitting element 10 and is composed of at least awavelength-converted material 221. When the semiconductor light-emittingstack 12 receives a current, it can emit a primary light. The primarylight enters the wavelength conversion structure 22 and then is absorbedby the wavelength-converted material 221 thereof to generate a convertedlight whose wavelength is different from that of the primary light.Because the wavelength-converted material 221 is unrestricted to onekind, the converted light can be of multiple colors. Before beingattached to the semiconductor light-emitting stack 12, the wavelengthconversion structure 22 is formed on a temporary substrate (not shownhere) and then is attached to the semiconductor light-emitting stack 12by the first attaching layer 13 so the process of encapsulating a chipcan be simplified and the thickness and quality of the wavelengthconversion structure 22 can be controlled easily. In addition, becausethe wavelength conversion structure 22 does not cover the opaquesubstrate 11, the opaque substrate 11 having high heat-dissipationefficiency can dissipate easily the heat from the semiconductorlight-emitting stack 12, and the performance of the semiconductorlight-emitting device 1 is promoted accordingly.

In the present embodiment, the wavelength conversion structure 22 caninclude only the wavelength-converted material 221 or be a non-gluewavelength-converted material structure. The non-gluewavelength-converted structure 22 is a conglomeration ofwavelength-converted materials without glue like paste, epoxy or otherglued adhesive materials. If the wavelength conversion structure 22 onlyincludes the wavelength-converted material 221, the method for gatheringthe wavelength-converted material 221 can include precipitation processor other physical deposition processes. The adhesion between thesemiconductor light-emitting stack 12 and the wavelength conversionstructure 22 can be increased by heating or pressing thewavelength-converted material 221. If the wavelength conversionstructure 22 is the non-glue wavelength conversion structure, the lightcan avoid being absorbed by glue so better wavelength conversionefficiency and color can be provided. In addition, adjusting thethickness of the wavelength conversion structure 22 and the distributionof the wavelength-converted material 221 can control the ratio ofconversion of the primary light. The primary light being not convertedand the converted light are mixed suitably to generate white light withbetter color rendering index.

In this embodiment, the wavelength-converted material 221 can bephosphor such as Y₃Al₅O₁₂. Moreover, the wavelength-converted material221 can also include Gd₃Ga₅O₁₂:Ce, (Lu,Y)₃Al₅O₁₂:Ce, SrS:Eu, SrGa₂S₄:Eu,(Sr,Ca,Ba)(Al,Ga)₂S₄:Eu, (Ca,Sr)S:Eu,Mn, (Ca,Sr)S:Ce,(Sr,Ba,Ca)₂Si₅N₈:Eu, (Ba,Sr,Ca)₂SiO₄:Eu, (Ca,Sr,Ba)Si₂O₂N₂:Eu, or II-VIgroup semiconductor. Preferably, it can be a non-insulating materialsuch as CdZnSe.

The first attaching layer 13 is located on the semiconductorlight-emitting stack 12 and attaches the semiconductor light-emittingelement 10 to the wavelength conversion structure 22. The firstattaching layer 13 can be epoxy, polyimide (PI), polyetherimide, PFCB,or other substitution. Preferably, it can be a transparent material suchas BCB. Basically, the first attaching layer 13 is a structure which isdoped no wavelength-converted material 221 intentionally and isindependent from other layers. However, the first attaching layer 13also can be doped with the wavelength-converted material 221 accordingto requirement. The semiconductor light-emitting device 1 furtherincludes a first electrode 14 and a second electrode 15. The firstelectrode 14 is located on the contact layer 125 and pierces thewavelength conversion structure 22 and the first attaching layer 13 toelectrically contact to the semiconductor light-emitting stack 12. Thesecond electrode 15 is formed under the opaque substrate 11 to form anelectrical circuit.

As shown in FIGS. 2-4, a manufacturing method of this embodimentstarting from a wafer form includes forming a wavelength conversionelement 20 including a wavelength conversion structure 22 and atemporary substrate 24; forming a semiconductor light-emitting element10 including a semiconductor light-emitting stack 12 and an opaquesubstrate 11; and attaching the wavelength conversion element 20 to thesemiconductor light-emitting element 10 by a first attaching layer 13 toform a semiconductor light-emitting structure 30, wherein the temporarysubstrate 24 can be kept or removed alternatively. A process such asetching is utilized to form a first electrode and a second electrode(not shown here) then. The semiconductor light-emitting structure 30 isprocessed to form a chip of the semiconductor light-emitting device 1shown in FIG. 1 by a dicing process. Referring to FIG. 5, the number ofthe chips is for representation only.

The wavelength conversion structure 22 is formed on the temporarysubstrate 24 by the method of precipitation, deposition, or growing thewavelength-converter material 221 thereon. If the wavelength conversionstructure 22 is formed by the wavelength-converter material 221 and anadhesive material, the semiconductor light-emitting device 1 can beformed by using the known lithography or photoresist lift-off method. Ifthe wavelength-converted material 221 is composed of II-VI groupsemiconductor only, lift-off process to remove the temporary substrate24 is preferable. Moreover, the wavelength-converted material 221 alsocan be coated on the temporary substrate 24 by printing. Theaforementioned deposition includes Chemical Vapor Deposition (CVD),Metal-organic Chemical Vapor Deposition (MOCVD), Vapor Phase Epitaxy(VPE), Liquid Phase Epitaxy (LPE), or Molecular Beam Epitaxy (MBE). Thetemporary substrate 24 can be transparent material or opaque material.If the temporary substrate 24 is opaque, it can be removed after thewavelength conversion element 20 is attached to the semiconductorlight-emitting element 10.

In another embodiment, comparing to the opaque substrate 11 and thewavelength conversion structure 22, the thickness of the semiconductorlight-emitting stack 12 is considerably thin. For example, the thicknessof the opaque substrate 11 is about 100 μm and that of the wavelengthconversion structure 22 is about 10 μm. However, the thickness of thesemiconductor light-emitting stack 12 is only about 3 μm. Thus, lesslight from the semiconductor light-emitting stack 12 emits laterally andthe probability of the primary light passing the wavelength conversionstructure 22 is increased.

Referring to FIG. 6, in another embodiment, a semiconductorlight-emitting device 2 includes the first electrode 14, the secondelectrode 15, the opaque substrate 11, the semiconductor light-emittingstack 12, the first attaching layer 13, and the wavelength conversionstructure 22. In addition, the semiconductor light-emitting device 2further includes a transparent conductive layer 16, a reflective layer17, a second attaching layer 18, and a protective structure 19. Thetransparent conductive layer 16 is located under the semiconductorlight-emitting stack 12 and is formed therewith. It can spread currentand form ohmic contact with other layers. The material of thetransparent conductive layer 16 includes ITO, CTO, ATO, ZnO, ZTO, Ni/Au,NiO/Au, TiWN, transparent metal layers, the combination thereof, orother substitute materials. The reflective layer 17 can be located on orunder the second attaching layer 18 according to the material thereof.The material of the reflective layer 17 can be metal, oxide, thecombination thereof, or other reflective materials. Preferably, itincludes In, Sn, Al, Au, Pt, Zn, Ag, Ti, Pb, Ge, Cu, Ni, AuBe, AuGe,AuZn, PbSn, SiN_(x), SiO₂, Al₂O₃, TiO₂, MgO, or the combination thereof.In addition, it also can be a DBR.

The second attaching layer 18 is located on the opaque substrate 11 andattaches the opaque substrate 11 to the semiconductor light-emittingstack 12. The second attaching layer 18 can be metal such as AuSn, InAg,InAu, In, Au, Al, Ag, or the alloy thereof. The second attaching layer18 is formed in-between the opaque substrate 11 and the semiconductorlight-emitting stack 12 by soldering to connect thereto at apredetermined temperature. It also can be a mirror to reflect the lightemitting to the opaque substrate 11 or an ohmic contact layer to formelectrical connection between the opaque substrate 11 and thesemiconductor light-emitting stack 12. The opaque substrate 11 isattached to the semiconductor light-emitting stack 12 under a suitablepressure such as 200 g/cm²˜400 g/cm² and a suitable temperature such as200° C.˜800° C., preferably 200° C.˜250° C. The second attaching layer18 also can be transparent and located on the reflective layer 17, andthe material thereof can be epoxy, polyimide, polyetherimide, PFCB, orother organic bonding materials, preferably BCB. It can be a structurewithout the wavelength-converted material 221 independent from otherlayers or be doped with the wavelength-converted material 221 accordingto requirement.

The protective structure 19 is formed on the wavelength conversionstructure 22 to protect the wavelength conversion structure 22 and otherstructures below from harm such as moisture or shock. The material ofthe protective structure 19 includes Su8, BCB, PFCB, epoxy, acrylicresin, COC, PMMA, PET, PC, polyetherimide, fluorocarbon polymer,silicone, glass, Al₂O₃, SiO₂, SiN_(x), TiO₂, the combination thereof, orother transparent materials. The protective structure 19 furtherincludes a plurality of optical layers 191 and 192. Each of them hasdifferent thickness to release the thermal stress of the protectivestructure 19 according to different conditions of the processes toprevent the protective layer 19 from crack. The first optical layer 191and the second optical layer 192 can be diffusers, concentrators, orother structures that adjust the illuminant characteristic of thesemiconductor light-emitting device 2.

Referring to FIGS. 7-9, a manufacturing method of this embodimentstarting from wafer form includes forming a semiconductor light-emittingstack 12, a transparent conductive layer 16, and a reflective layer 17on a growth substrate 41 to form a semiconductor element 40; attachingan opaque substrate 11 to the semiconductor element 40 by a secondattaching layer 18; removing the growth substrate 41 to form asemiconductor light-emitting element 50; attaching the semiconductorelement 50 to a wavelength conversion element 20 shown in FIG. 2 by afirst attaching layer 13 to form a semiconductor light-emittingstructure 60, wherein a temporary substrate 24 of the wavelengthconversion element 20 can be kept or removed alternatively. If thetemporary substrate 24 is transparent, it can be kept as the protectivestructure 19. The semiconductor light-emitting structure 60 is processedto form a chip of the semiconductor light-emitting device 2 by a dicingprocess. Referring to FIG. 10, the number of the chips is forrepresentation only. If the second attaching layer 18 is formed on thetransparent conductive layer 16 or the reflective layer 17, it istransparent. However, the reflective layer 17 also can be formed on theopaque substrate 11.

Referring to FIG. 11, in another embodiment, a semiconductorlight-emitting device 3 includes an opaque substrate 31, a semiconductorlight-emitting stack 32, a first attaching layer 33, a first electrode34, a second electrode 35, a transparent conductive layer 36, areflective layer 37, a second attaching layer 38, and a wavelengthconversion structure 42. The first electrode 34 and the second electrode35 are on the same side of the opaque substrate 31. The opaque substrate31 includes a reflective layer 37 located on a base 311. The reflectivelayer 37 can reflect the light emitting to the base 311 to thewavelength conversion structure 42 without passing the base 311 when thesecond attaching layer 38 is transparent. On the other hand, thereflective layer 37 can also be located in-between the second attachinglayer 38 and the transparent conductive layer 36.

Referring to FIGS. 12-18, a manufacturing method of this embodimentstarting from the wafer form includes forming a semiconductor element70, including forming a semiconductor light-emitting stack 32 on agrowth substrate 71 as shown in FIG. 12; forming a temporary attachinglayer 82 on a transient substrate 81 as shown in FIG. 13; attaching thetransient substrate 81 to the semiconductor element 70 by the temporaryattaching layer 82 as shown in FIG. 14; removing the growth substrate71; forming a transparent conductive layer 36 on the semiconductorlight-emitting stack 32 as shown in FIG. 15; attaching the semiconductorlight-emitting stack 32 and the transparent conductive layer 36 to anopaque substrate 31 including a reflective layer 37 by a secondattaching layer 38; removing the transient substrate 81 and thetemporary attaching layer 82 as shown in FIG. 16; forming a wavelengthconversion element 80 including a wavelength conversion structure 42located on a temporary substrate 44; and attaching the wavelengthconversion element 80 to the semiconductor light-emitting stack 32 by afirst attaching layer 33 to form a semiconductor light-emittingstructure 90 as shown in FIG. 18. The semiconductor light-emittingstructure 90 is processed to form a chip of the semiconductorlight-emitting device 3 by a dicing process. Referring to FIG. 19, thenumber of the chips is for representation only. The temporary substrate44 can be kept or removed alternatively. If it is a transparentsubstrate, it can be kept as a protective structure.

FIG. 20 shows a schematic view of a light source device 5. It includes asemiconductor light-emitting device as disclosed in each of theseembodiments of the present invention. The light source device 5 can bean illuminating device such as a streetlight, a vehicle light, or indoorlight source, a traffic light, or a backlight source of a backlightmodule of a panel display. The light source device 5 includes a lightsource 51 composed of an aforementioned semiconductor light-emittingdevice, a power supply system 52 offering a current to the light source51, and a control element 53 to control the power supply system 52.

FIG. 21 shows a schematic view of a backlight module 6. It includes theaforementioned light source device 5 and an optical element 61. Theoptical element 61 processes the light form the light source device 5 toapply to the panel display. For example, the optical element 61 candiffuse the light from the light source device 5.

It should be noted that the proposed various embodiments are not for thepurpose to limit the scope of the invention. Any possible modificationswithout departing from the spirit of the invention are covered by theappended claims.

1. A semiconductor light-emitting device, comprising: a semiconductorlight-emitting stack having a first side and a second side opposite tothe first side; a wavelength conversion structure arranged on the firstside; a first attaching layer, doped with a wavelength-convertedmaterial, arranged between the semiconductor light-emitting stack andthe wavelength conversion structure; and a reflective layer arranged onthe second side.
 2. The semiconductor light-emitting device of claim 1,further comprising an opaque substrate arranged on the reflective layer.3. The semiconductor light-emitting device of claim 1, furthercomprising a protective structure covering the wavelength conversionstructure.
 4. The semiconductor light-emitting device of claim 1,further comprising a plurality of optical layers covering the wavelengthconversion structure.
 5. The semiconductor light-emitting device ofclaim 1, further comprising: an opaque substrate arranged on the secondside; and a second attaching layer arranged between the opaque substrateand the semiconductor light-emitting stack.
 6. The semiconductorlight-emitting device of claim 1, further comprising: a second attachinglayer doped with a wavelength-converted material and arranged betweenthe reflective layer and the semiconductor light-emitting stack.
 7. Asemiconductor light-emitting device, comprising: a semiconductorlight-emitting stack having a first side and a second side opposite tothe first side; a protective structure arranged on the first side; awavelength conversion structure formed by a mixture of awavelength-converted material and an adhesive material; and a firstattaching layer; wherein the wavelength conversion structure and thefirst attaching layer are arranged between the semiconductorlight-emitting stack and the protective layer.
 8. The semiconductorlight-emitting device of claim 7, further comprising: a reflective layerarranged on the second side for reflecting light from the semiconductorlight-emitting stack towards the first side.
 9. The semiconductorlight-emitting device of claim 7, further comprising: an opaquesubstrate; and a reflective layer arranged between the opaque substrateand the semiconductor light-emitting stack.
 10. The semiconductorlight-emitting device of claim 7, further comprising: a reflectivelayer; and a second attaching layer arranged between the reflectivelayer and the semiconductor light-emitting stack.
 11. The semiconductorlight-emitting device of claim 7, wherein the protective structure, thewavelength conversion structure, and first attaching layer have widths,and at least two of the widths are substantially the same.
 12. Thesemiconductor light-emitting device of claim 7, wherein the protectivestructure has a right surface and a left surface parallel to the rightsurface.
 13. The semiconductor light-emitting device of claim 7, whereinthe protective structure comprises a transparent material selected fromthe group consisting of Su8, BCB, PFCB, epoxy, acrylic resin, COC, PMMA,PET, PC, polyetherimide, fluorocarbon polymer, silicone, glass, Al₂O₃,SiO₂, SiN_(x), and TiO₂.
 14. A semiconductor light-emitting device,comprising: a semiconductor light-emitting stack having a first side anda second side opposite to the first side; a wavelength conversionstructure having an opening and arranged on the first side; a firstattaching layer attached to the wavelength conversion structure; and aprotective structure covering the wavelength conversion structure andhaving a width substantially equal to that of the first attaching layer.15. The semiconductor light-emitting device of claim 14, furthercomprising a reflective layer arranged on the second side.
 16. Thesemiconductor light-emitting device of claim 14, further comprising: anopaque substrate arranged on the second side; and a reflective layerarranged between the opaque substrate and the semiconductorlight-emitting stack.
 17. The semiconductor light-emitting device ofclaim 14, wherein the protective structure has a right surface and aleft surface parallel to the right surface.
 18. The semiconductorlight-emitting device of claim 14, wherein the protective structure hasa flat upmost surface.
 19. The semiconductor light-emitting device ofclaim 14, wherein the wavelength conversion structure comprises one ormore wavelength-converted materials.